1. Field of the Invention
The invention relates to the cleaning of tapping pipes used in reduction cells of aluminium smelters.
2. Prior Art
Molten aluminium is tapped from reduction cells in the aluminium smelting industry using vacuum-assisted tapping pipes (also known as tapping siphons or tapping tubes) into either sealed or open crucibles (or ladles). Older-generation tapping pipes, for use with either sealed open crucibles, are usually curved (or otherwise bent) in profile whereas more recent technologies, over the last twenty years or so, normally utilise straight tapping pipes with sealed crucibles.
Within the reduction cell (also known as a smelting pot) the molten aluminium is below the molten electrolyte known as bath (which is principally comprised of cryolite). In tapping the aluminium, there is inevitably some pick-up of bath and after several uses a build-up of frozen bath, and some aluminium, is left within the tapping pipes. This renders the tapping pipes ineffective and requires that they be regularly cleaned.
Curved tapping pipes have in the past been cleaned using a mechanism known as a pneumatic rattler. This is in the form of a small pneumatic motor with a swiveling head attached to a pneumatic hose, which is fed trough the pipe manually. This is an extremely noisy and dusty operation which is considered unacceptable in today""s smelters.
Straight tapping pipes are usually cleaned by automatic tapping pipe cleaning machines which utilise a long straight drill rod with some form of cutter head, rotated by an electric or hydraulic drive, and which is fed forward by an electric, pneumatic or hydraulic mechanism. Some designs of these machines have a longitudinal hole in the centre of the drill rod to allow compressed air to be channelled to the cutter head. This air serves the dual functions of purging debris away from the workface and cooling the cutter head.
Problems with automated cleaning of curved pipes have been the requirement to transmit sufficient torque to a cutter head to remove the bath/metal build-up and to be able to channel air to the cutter head.
According to the present invention, there is provided a drill rod for clearing obstructing material from the interior of a tapping pipe used for evacuation of aluminium from a reduction cell of an aluminium smelter by drilling, wherein the drill rod is flexible, whereby it may drill obstructing material from said tapping pipe, through a bend in the tapping pipe.
The invention further provides apparatus for drilling obstructing material from within a tapping pipe of a reduction cell of an aluminium smelter, having:
a) means for mounting the pipe substantially fixedly;
b) a drilling rod having a cutting head;
c) means for rotating the drilling rod for rotating said cutting rod;
d) means for axially advancing the drilling rod to cause the cutting head and drilling rod to pass into the interior of the tapping pipe for effecting said drilling, wherein said drilling rod is, over at least a portion thereof adjacent to the cutting head, capable of bending whereby it may, while effecting said cutting, pass through a bend in the tapping pipe.
The invention also provides a method for removing material from a tapping pipe comprising passing thereinto a rotating drilling rod having a cutting head whereby to cause the cutting head to clear said obstructing material by drilling, and in which the drilling rod is at least partially bendable, while transmitting cutting torque to the cutting head to accommodate a bend in the pipe.
The invention also provides rotary device having links coupled together for rotation about a lengthwise device axis, coupling between an adjacent pair of said links being provided by coupling means which couples the adjacent links together for permitting substantially universal movement with respect to each other transversely to said device axis, the coupling means permitting relative displacement between the adjacent links whereby the axial length presented by the adjacent links can be varied between relatively compressed and relatively uncompressed lengths, the coupling means, when the adjacent links are displaced to the condition where the relatively compressed length prevails, at least relatively limiting the degree of said substantially universal movement permitted as between the adjacent links.